Hall probe for measuring an axial magnetic field in a bore

ABSTRACT

Four molybdenum wires are embedded in a hardened glass rod having a small diameter and resistant to extreme temperature changes. Each of the wires has an end at an axial end surface of the rod coplanar with such surface. A layer of semiconductor material of specific configuration on the end surface of the rod covers the wire ends and has a temperature coefficient of the Hall voltage and the electrical specific resistance which is less than or equal to 0.1 percent per degree Centigrade.

Unite if:

States atent Freller et a1.

[ 51 May 23,1972

. Int. Cl

HALL PROBE FOR MEASURING AN AXIAL MAGNETIC FIELD IN A BORE HelmutFreller; Magdalena Obitz, both of Nuremberg, Germany SiemensAktiengesellschatt, Berlin, Germany I July 1, 1969 Inventors:

Assignee:

Filed:

Appl. No.:

Foreign Application Priority Data July 12, 1968 Germany ..P 17 66 756.6

us. Cl. ..338/32 R, 324/45 ..H01c 7/16 338/32; 307/309; 317/235;

Field of Search References Cited UNITED STATES PATENTS Shaper ..324/45McMaster et al ..324/45 FOREIGN PATENTS OR APPLICATIONS 785,251 10/1957Great Britain; ..324/45 OTHER PUBLICATIONS Bell lnc., High SensitivityGaussmeter, Model 120, Form No. l-1SG566 Primary Examiner-Rodney D.Bennett, Jr.

Assistant Examiner-R. Kinberg Attorney-Curt M. Avery, Arthur E. Wilfond,Herbert L. Lerner and Daniel .1 Tick ABSTRACT 8 Claims, 3 DrawingFigures HALL PROBE FOR MEASURING AN AXIAL MAGNETIC FIELD IN A BOREDESCRIPTION OF THE INVENTION The present invention relates to a Hallprobe. More particularly, the invention relates to a Hall probe formeasuring an axial magnetic field in a bore. The Hall probe of thepresent invention has a small diameter and is resistant to extremetemperature variations.

A small diameter" is intended to be a diameter equal to or less than 2mm. The Hall probe of the present invention is resistant to extremetemperature changes, and therefore no irreversible changes in thecharacteristics of said Hall probe will occur within a temperature rangeof 273 to +200 C.

In cryogenics, particularly during the investigation of superconductoreffects, it is often necessary to measure magnetic fields inside smallbores at low temperatures. Hall generators or devices provide goodresults in measuring magnetic fields at normal temperatures and specialdesigns of Hall generators are accurate in measuring magnetic fields athigh and low temperatures. When Hall generators having vapor-depositedsemiconductor layers are utilized, however, bores having diameters ofless than 2 mm create considerable difficulties in permitting thepositioning or placement of the four terminal contacts of the Halldevice on the active semiconductor layer. These difficulties areconsiderably increased by the requirement that the Hall device have asatisfactory resistance to temperature variations of its contacts withina temperature range of 273 to +200 C. It has thus been impossible toproduce Hall probes having satisfactory characteristics, includingdiameters of less than or equal to 2 mm for utilization in a temperaturerange of 273 to +200 C.

' The principal object of the present invention is to provide a new andimproved Hall probe for measuring an axial magnetic field in a bore.

An object of the present invention is to provide a Hall probe formeasuring an axial magnetic field in a bore, which probe overcomes thedisadvantages of known probes of similar type.

An object of the present invention is to provide a Hall probe formeasuring an axial magnetic field in a bore with accuracy, efficiencyand reliability.

An object of the present inventionis to provide a Hall probe formeasuring an axial magnetic field in a bore, which probe is resistant totemperature changes within a temperature range of 273 to +200 C.

An object of the present invention is to provide a Hall probe formeasuring an axial magnetic field in a bore, which probe has a diameterless than or equal to 2 mm.

An object of the present invention is to provide a Hall probe formeasuring an axial magnetic field in a bore, which probe is of simple,but effective, structure and is produced and operated with facility.

In accordance with the present invention, a Hall probe for measuring anaxial magnetic filed in a bore comprises a small rod of electricallyinsulating material having a small diameter and resistant to extremetemperature changes. The rod has an axial end surface. Four wires areembedded in the rod. Each wire has an end at the end surface of the rod.The wire ends and the end surfaces are coplanar. A layer ofsemiconductor material of specific configuration is provided on the endsurface of the rod and covers the wire ends. The wire ends are inelectrical contactwith the layer of semiconductor material. Thesemiconductor material has a temperature coefficient of the Hall voltageand the electrical specific resistance which is less than or equal to0.1 percent per degree Centigrade.

The rod comprises hardened glass. Each of the wires comprisesmolybdenum. Each of the wires has a diameter in the range of 0.05 to 1.0mm. The wire ends are at the points of a square on the end surface ofthe rod.

The layer of semiconductor material has a thickness of 0.5 to 3.0micrometers and comprises indium arsenide.

In order that the present invention may be readily carried into effect,it will now be described with reference to the accompanying drawing,wherein:

FIG. 1a is a view of an embodiment of a Hall probe of the presentinvention for measuring an axial magnetic field in a bore;

FIG. 1b is a sectional view taken along the lines Ib-lb if FIG. la; and

FIG. 2 is an end view taken along the lines 11-" of FIG. la.

In FIGS. la and lb, four molybdenum wires 12, spaced from each other atthe four corners or points ofa square, are embedded in a small rod 11 ofhardened glass. Each of the wires 12 has a diameter of 0.05 to 0.1 mm.The corresponding wire end of each of the molybdenum wires 12 ispositioned at, and coplanarly with, an end surface 21 of the rod 11.

As shown in FIG. 2, a layer 23 of semiconductor material such as, forexample, indium arsenide, is vapor-deposited on the end surface 21 ofthe rod 11. Other suitable semiconductor materials, which have atemperature coefficient of the Hall voltage and the electrical specificresistance which is les than or equal to 0.1 percent per degreeCentigrade, are indium antimonide and germanium. The layer 23 ofsemiconductor material covers the wire ends of the wires 12 and has athickness of 0.5 to 3.0 micrometers. The layer of semiconductor material23 is vapor-deposited at a pressure of approximately 10 Torr at an endsurface temperature in a range between 600 and 700 C. I

The vapor-deposited layer of semiconductor material 23, as shown in FIG.2, is of specific configuration, and covers the wire ends 22 of thewires 12. The specific configuration of the semiconductor material 23 isprovided by a subsequent etching process and is a configuration which isusual for Hall probes, as shown in FIG. 2. In FIG. 2, the end surface 21of the rod 11 is that of hardened glass, since the etching process hasremoved the semiconductor material 23 therefrom.

Hardened glass is preferably utilized as therod ll, molybdenum ispreferably utilized as the wires 12 and indium arsenide is preferablyutilized as the semiconductor material 23. This is due to the fact thatthese three materials have almost the same expansion coefficient withina wide temperature range, so that there is excellent adhesion betweenthe semiconductor layer and the molybdenum and glass. This providesexcellent stability for the electrical properties of the Hall probeduring abrupt, sharp or extreme temperature variations.

In the Hall probe of the present invention, the vapordepositing processsimultaneously includes all the contacting processes utilized in theproduction of a Hall device or generator. This is due to the fact that acorresponding end of each of the molybdenum wires 12 is in closeelectrical contact with the layer of semiconductor material 23 and theother ends of said wires protrude at the other end of the glass rod 11.The Hall probe thus provides the necessary terminal wires.

The Hall probe of the present invention may be provided, withoutdifficulty, with diameters equal to or less than l.0 mm. The utilizationof glass as the rod 11 and the utilization of molybdenum as the wires12, provides stability up to temperatures of 700 C and permits thevapor-deposition of very sensitive indium arsenide layers. Thesensitivity of the Hall probes may thus be V K0202 (m wherein K0 is thesensitivity of the Hall probes, V is volts, A is amperes and k6 iskilogauss.

While the invention has been described by means of a specific exampleand in a specific embodiment, we do not wish to be limited thereto, forobvious modifications will occur to those skilled in the art withoutdeparting from the spirit and scope of the invention.

We claim:

1. A Hall probe for measuring an axial bore, comprising a rod ofelectrically insulating material resistant to temperature changes, saidrod having an axial end surface;

four wires embedded in said rod each having an exposed end at the endsurface of said rod, the wire ends and said end surface being coplanar;and

magnetic field in a a layer of semiconductor material on the end surfaceof said rod covering said wire ends and in electrical contact therewith,said semiconductor material having a temperature coefficient of the Hallvoltage and the electrical specific resistance which is less than orequal to 0.1 percent per degree Centigrade.

2. A Hall probe as claimed in claim 1, wherein said rod compriseshardened glass.

3. A Hall probe as claimed in claim 1, wherein each of the wirescomprises molybdenum.

4. A Hall probe as claimed in claim 1, wherein each of the wires has adiameter in the range of 0.05 to 1.0 mm.

5. A Hall probe as claimed in claim 1, wherein said wire ends are at thepoints of a square on the end surface of said rod.

6. A Hall probe as claimed in claim 1, wherein said layer ofsemiconductor material has a thickness of 0.5 to 3.0 micrometers.

7. A Hall probe as claimed in claim 1, wherein said layer ofsemiconductor material comprises indium arsenide.

8. A Hall probe as claimed in claim I; wherein said rod compriseshardened glass, each of said wires comprises molybdenum and has adiameter of 0.05 to 1.0 mm and said semiconductor material comprisesindium arsenide having a thickness of 0.5 to 3.0 micrometers.

F-4l74 P e UNTTEE STATES PATENT oEETcE CEREIIHCATE 0E coEEEcTToN PecentNO- 3, D t d y 3,

Inventor s HELMUT FRELLER et 1 It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

T" v I In the heading tothe printed specification, the name and addressof the assignee should read --Siemens Aktiengesellschaft,

Berlin und Nifinchen, Germany-- Signed and sealed this 10th day of April1973 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer v Commissionerof Patents F-al m w g UNITED STATES PATENT ()FFICE CERTKFHCATE @FCQRREC'MQN Dated May 23, 197

HELMUT FRELLER et a1 Patent No.

Inventor(s) It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

In the heading tethe printed specification, the name and address of theassignee should. read --Siemens Aktiengesellschaft,

Berlin und Nylfinchen, Germany- Signed and sealed this 10th day of April1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Commissioner of PatentsAttesting Officer

2. A Hall probe as claimed in claim 1, wherein said rod compriseshardened glass.
 3. A Hall probe as claimed in claim 1, wherein each ofthe wires comprises molybdenum.
 4. A Hall probe as claimed in claim 1,wherein each of the wires has a diameter in the range of 0.05 to 1.0 mm.5. A Hall probe as claimed in claim 1, wherein said wire ends are at thepoints of a square on the end surface of said rod.
 6. A Hall probe asclaimed in claim 1, wherein said layer of semiconductor material has athickness of 0.5 to 3.0 micrometers.
 7. A Hall probe as claimed in claim1, wherein said layer of semiconductor material comprises indiumarsenide.
 8. A Hall probe as claimed in claim 1, wherein said rodcomprises hardened glass, each of said wires comprises molybdenum andhas a diameter of 0.05 to 1.0 mm and said semiconductor materialcomprises indium arsenide having a thickness of 0.5 to 3.0 micrometers.